Stator core structure and manufacturing process and industrial development-Xinda Motor- electric motors and EV accessories supplier|INDEX--

Stator core structure and manufacturing process and industrial development

Date：2023-03-15　　　Author：Shandong Xinda Motor Co., Ltd.

Stator core structure and manufacturing process

The stator core is composed of sector pieces, ventilation slots, positioning ribs, upper and lower teeth pressure plates, tension bolts and supporting plates and other parts. The stator core is made of silicon steel sheets punched into fan-shaped pieces and stacked on the positioning ribs. The positioning ribs are welded to the frame ring plate through the supporting plate, and the core is compressed into a whole through the upper and lower tooth pressure plates with tension bolts. The iron core is also the part where the winding is placed. When the generator is running, the iron core will be subjected to the combined effects of mechanical force, thermal stress and electromagnetic force. At present, most of the stator cores adopt floating double dovetail rib structure, mainly to eliminate the negative effect caused by the thermal expansion of the stator core and prevent the core from warping and deforming. According to the structural characteristics of the stator core compression, it can be divided into a core-through structure and a back-pull structure.

Back-pull bolt structure: the compression bolt is on the back of the iron core, and is supported by the top wire at the end of the pressure plate to transmit the compression force of the bolt to the iron core. The structure is relatively complicated, and the compression process is cumbersome. It is necessary to adjust the compression bolt and top wire back and forth Use the jacking wire to adjust the levelness of the pressure plate. The gap between the pressing bolt and the back of the iron core should be ensured, which is generally required to be more than 2mm; otherwise, the radius and appearance of the stator core will be affected when the bolt is tightened. Influence, such as the wrong teeth of a few punching pieces in the groove of the iron core, the upper part of the inner diameter of the iron core becomes smaller, and the verticality of the iron core changes.

Through-core bolt structure: the compression bolt passes through the center of the iron core punching sheet, and directly applies the compression force to the iron core. Its structure and compression method are relatively simple, but the compression bolt needs to be insulated from the stator frame and the iron core. , the insulation protection is more complicated and difficult, and after the unit has been in operation for a long time, the insulation is easily damaged, causing the through-hole bolts to conduct heat, which affects the stable operation of the unit.

Picture above (left): Back-pull bolt compression structure diagram

Picture above (right): Structural diagram of through-hole bolt compression

The main raw material of the stator core is silicon steel sheet, which is generally divided into hot rolling and cold rolling in China. The main manufacturing process of the stator core includes the steps of stamping, insulation, pressing, welding and other steps of silicon steel sheet. The stamping process includes the steps of cutting silicon steel sheet and punching, among which punching is divided into single punching, re-punching and progressive punching.

Above: Advantages and disadvantages of different punching methods

The insulation treatment of the punching sheet mainly includes two methods: varnish insulation and oxidation insulation. The painting process is mainly composed of two parts: painting and drying, which are completed on the painting machine at the same time. The commonly used insulating paint for silicon steel sheets in China is 1611 oily paint, which has good oil and water resistance, high insulation resistance, and is compatible with adhesives. Good performance; currently the most widely used in the market is the three-stage paint machine. Oxidation and insulation treatment of the punching sheet is artificially formed on the surface of the punching sheet to form a uniform and firm ferric oxide or ferric oxide film. After the insulation treatment of the stamped sheet is completed, the quality of the insulation treatment should be inspected, including three steps: appearance observation, paint film thickness measurement, and insulation resistance measurement.

Picture above (left): Silicon steel sheet, punched sheet water-soluble paint coating and drying line

Picture above (right): Rotor punching structure diagram

The three main process parameters of the core pressing process are pressure, core length and core weight, which affect each other and jointly determine the performance of the core. Under the premise of ensuring the length of the iron core, the pressure is positively correlated with the number of punched pieces pressed, the tighter the iron core is pressed, the greater its weight, and the weight further affects the length of the iron core, which in turn affects the magnetic flux density of the iron core, and finally determines the size of the iron loss. The last step in stator core processing is to weld the electronic core into shape by laser welding. Motor stator laminations are generally made of cold-rolled or hot-rolled silicon steel sheets, which have good weldability and are suitable for laser welding.

Picture above (left): Stator core structure with external pressure mounting

Above (right): Motor stator core laser welding system

The demand for driving motor drives the development of the industry

Stator core manufacturing is in the growth stage of the industry. From a structural point of view, the motor is mainly composed of a stator and a rotor. The stator mainly consists of a stator core, a stator winding, and a machine base. The stator core is the core component of the stator. The material quality and size of the stamping sheet And shape and position accuracy, burr disposal and lamination are closely related to the manufacturing cost of the motor. According to the statistical data of "Motor Technology", the value of the stator accounts for about 19% of the total value of motor parts, and the cost of the drive motor is relatively high. At present, with the rapid increase in the installed capacity of drive motors, the demand for stator cores has increased year-on-year. However, the industry is still in the growth stage in general. The growth in downstream demand drives the development of the stator core industry. The number of enterprises in the industry is on the rise, and the overall profitability of the industry remains stable. Steady growth, but market concentration needs to be further strengthened.

Picture above (left): drive motor cost composition

Picture above (right): The physical picture of the stator core

The trend of specialized production is obvious. At the beginning of the 12th century, with the continuous enrichment and optimization of the downstream product structure and the continuous increase of downstream demand, the company began to continuously optimize the stator core production process and professional equipment, speeding up the specialized production process, and the product series expanded from low-voltage products to high-voltage products. , low-voltage and high-power products, and stator core products for generators, the business model has changed from processing with supplied materials to an independent production and sales model; from the beginning of the 21st century to the present, with the entry of internationally renowned motor factories and the improvement of stator core production technology in my country, domestic substitution, The trend of product export is becoming more and more obvious, and the trend of specialized production is becoming more and more obvious. In 2021, it is estimated that the national new energy vehicle drive motor market size will reach 19.13 billion yuan, and it is expected that the high prosperity of the industry will continue to be maintained.

Stator core industry recommended target

Xinzhi Group

The domestic veteran motor rotor leader is actively deploying new businesses. The company, formerly known as Xinzhi Electric, was founded in 1990 and is the largest supplier of stators and rotors for automobile engines in China. It was listed on the Shenzhen Stock Exchange on March 16, 2012. Based on the main business of auto parts, the company is actively developing new energy vehicle business. The company's products mainly include automotive generator stators and assemblies, micro-special motor rotors, etc. The company keeps up with the market and actively develops the flat wire motor business. At present, the fork type flat wire technology is mainly used, and mass production has been formed. In addition, the company is also vigorously promoting the construction of new energy motor production capacity. In October 2021, the company's new energy stator and rotor assembly project with a total investment of nearly 1 billion yuan was signed in Pujiang County, Chengdu and started construction. After the project is completed, it will reach an annual production capacity of 1 million sets of new energy stator and rotor assemblies. The main customers of the company's new energy business include BYD, UMC, Wei Xiaoli, Geely, Shanghai Electric Drive, Dongfeng Electric Drive, etc. In 2021Q1-Q3, the company achieved operating income of 2.74 billion yuan, a year-on-year increase of 6.28%, and net profit attributable to the parent company of 135 million yuan, a year-on-year decrease of 21.80%.

Picture above (left): Xinzhi Group’s operating income

Picture above (right): Xinzhi Group’s net profit status

Longsheng Technology

The motor iron core business has rapidly increased in volume, and actively seized the iron core market. Founded in 2004, the company is mainly engaged in the production and sales of automotive EGR systems. It is a leading domestic light-duty diesel vehicle EGR company and was listed on the Shenzhen Stock Exchange in 2017. In 2018, the company acquired Weiyan Precision and began to get involved in the motor core business. In October 2020 and November 2021, the company will expand the new energy vehicle drive motor core and natural gas injection rail assembly projects twice, officially extending to the field of new energy vehicles. The main customers of the company's new energy vehicle business include United Automotive Electronics, Weilai, GM, Volkswagen, GAC New Energy, Dianca, Japanese customers, a foreign-funded electric vehicle company and an energy company, etc. In 2021Q1-Q3, the company realized operating income of 807 million yuan, a year-on-year increase of 31.60%, and net profit attributable to the parent company of 67 million yuan, a year-on-year decrease of 5.60%.

Picture above (left): Longsheng Technology’s operating income

Picture above (right): Longsheng Technology’s net profit status

Zhenyu Technology

The proportion of motor iron core has increased, achieving a new growth curve. In 1994, the company started with the production of stamping dies, and landed on the Science and Technology Innovation Board in 2020. In 2013, the company established a subsidiary Suzhou Fansite Machinery Technology Co., Ltd. to provide customers with precision structural parts motor cores, and has since entered the field of motor cores. The main customers of the company's iron core business include Valeo Siemens, United Automobile Department, BYD Department, Suzhou Langgao, Dayang Department, Taicang Ten-speed and other professional manufacturers of motor parts. In 2022, the company will invest 1.2 billion yuan and 1 billion yuan in the construction of motor core and component manufacturing projects twice, which will improve the company's production capacity in the field of motor core parts manufacturing. The production capacity of the core business is expected to be gradually released in the next few years. The company's performance continued to increase at a high rate and added new impetus. In 2021 Q1-Q3, the company realized operating income of 4.011 billion yuan, a year-on-year increase of 107.33%, and net profit attributable to the parent company of 135 million yuan, a year-on-year increase of 14.41%.

Picture above (left): Zhenyu Technology’s operating income

Picture above (right): Zhenyu Technology’s net profit status

Stator core structure and manufacturing process and industrial development

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